Villagers found their bodies hanging from a tree in a nearby orchard the following morning.

Speaking through an interpreter, Jeevan Lal, the father of one of the victims, said: "We were ready to go to the police station after the girls hadn't returned, and the police officer came to me and said that the girls are hanging from a tree."

Budaun's superintendent of police, Maan Singh Chauhan, said an autopsy confirmed the two cousins, who were from a low-caste Dalit community, were raped and died from the hanging.

DNA samples have also been taken to help identity the perpetrators.

The victims' families say five men were responsible for the gruesome murders and have accused local police of shielding the attackers and refusing to take action when the girls were first reported missing.

It was only after villagers took the corpses to a nearby highway and blocked it in protest that anything was done.

Mr Singh Chauhan says police will eventually find the men responsible.

"Whatever happened, it was very wrong. It is a very serious issue," he told an interpreter.

"We are fully prepared and we are with the victim's family. We will take the strictest action against the culprits."

Rape culture

The aid organisation CARE Australia has called for cultural change in India to reduce the incidence of rape and violence against women in the wake of the latest attack.

"We need to change the culture that allows these things to happen," Ms Newton-Howes told Radio Australia.

"But that can be a long-term issue and there are more immediate things that we can do to bring about change."

Ms Newton-Howes says women need safe access to public facilities, first and foremost.

"The report suggests that these two girls were attacked when they left their homes to basically go to the toilet in an orchard nearby because there was no toilet in their own house," Ms Newton-Howes said.

"Access to facilities like safe toilets for girls makes a huge difference to others' ability to attack them.

"And so, really, access to good sanitation could make a huge difference to people such as these two girls."

Sex crimes against women, girls in India widespread: 2013 report

Activists say sex crimes against women and young girls are widespread in India.

A report by the Asian Centre for Human Rights (ASHR) in April last year said 48,338 child rape cases were recorded in India from 2001 to 2011.

The ASHR says the annual number of reported cases rose fourfold over that period.

Associate Professor Davleena Ghosh from the University of Technology in Sydney says law enforcement is part of the problem.

"The usual sort of joke amongst women in India is that if you get raped, you don't go to the police station because you'll just get raped again," Professor Ghosh said.

Women's whole status as a carrier of honour and shame within south Asian cultures [is] one of the major reasons why often women are assaulted.

Associate Professor Davleena Ghosh

"And the police [officer] is often the last person you would go to if you've had some form of sexual violence against you.

"Very often the police will not even accept first information reports or will refuse to do so if they have some connection with other people, and they will blame the woman for in fact being a loose woman or a prostitute."

Professor Ghosh says it is common for girls in the low-caste Dalit community to be targeted.

"A lot of women who go to get water, especially Dalit women, are often harassed and sexually violated in those sort of situations," she said.

"This is because they have to go long distances to get water from water sources which are not used by higher-caste Hindus.

"So there's just no ... safe or private places for women to be alone or to be safe in rural areas, or [it is] very difficult to ... be safe in rural areas."

Such incidents are common across the subcontinent. In December 2012, the fatal gang rape of a female student in New Delhi triggered public outrage and large anti-violence demonstrations.

The incident prompted the Indian government to pass tougher new laws to punish sex crimes.

Now, the Pakistani prime minister Nawaz Sharif has demanded to know why police there apparently stood by and did nothing.

Professor Ghosh says although it is still early days in the Uttar Pradesh case, there are broad similarities.

"Women's whole status as a carrier of honour and shame within south Asian cultures [is] one of the major reasons why often women are assaulted - not just [for the sake of] the sexual violence but also because they represent a way of revenge for other reasons," she said.

There is hope the international outrage will make a difference, but Professor Ghosh says with "an entrenched attitude of misogyny" in India, any change is likely to be slow.

"This sort of sexual violence is common. It may very well be increasing or it may be being better reported and the tolerance level of it is relatively high."